The present invention relates to a method for efficiently culturing fungous mycelia to be presented for food use.
It is well known that the mycelia of matsutake (Trrcholoma matsutake), shiitake (Lentinus edodes), mushroom (Agaricus campestris), honshimeji (Lyophyllum aggregatum), hatsutake (Lactarius hatsudake), enokitake (Flammuline velutipes), nameko (Pholiota nameko) and others belonging to the order of Agaricales are generally served for food use and the production method thereof includes the mycelium liquid culturing method.
While this liquid culturing method is conducted usually in a culturing medium containing 50 g/liter of sucrose, 10 g/liter of nitrate-type nitrogen, 5 g/liter of sodium phosphate, 2.5 g/liter of magnesium sulfate and 0.2 g/liter of iron sulfate in a stationary condition, such a method cannot be employed as a mass production method because, in addition to the low productivity, a large man power is required for the recovery of the mycelia and the efficiency for recovery is low.
Furthermore, it is essential in this method for food use to remove the culture medium which contains ingredients having adverse influences on human body such as nitrates.
Besides, there is known a solid culturing method by utilizing bagasse of sugarcane. This method, however, is defective because a complicated treatment must be undertaken for separation of the mycelia in addition to a long term of 2 to 3 months required for obtaining a sufficient amount of the mycelia. Moreover, contamination of the fungus is sometimes found in this method so that it is a difficult matter in utilization of the mycelia as a food to secure safety by preventing occurrence of mold poison and the like. Therefore, it is usual to grow mycelia by utilizing the solid culturing method followed by generation of fruiting bodies by means of a further temperature control, which are served usually as a food on the market but there remains a serious problem in respect of safety in order to be served as such for food use because fruiting bodies in general exhibit large absorption of poisonous metals contained in agricultural chemicals and culture medium as well as heavy accumulation thereof.
The present invention has been completed with an object to efficiently culture a fungus belonging to the order of Agaricales such as mushroom by using a liquid culture medium in such a way of production that the mycelia separated from the culture medium and the culture liquid as such can be served for food use.
The inventors continued extensive investigations on the liquid culturing method of fungi and, as a result, previously proposed a method in which a liquid culture medium containing sucrose or a sucrose-containing material as the carbon source is inoculated with a desired fungus to effect culturing with continued bubbling of a sterilized air containing oxygen in a high concentration [International Publication No. WO 00/65029 (published Nov. 20, 2000)] and, after further continued investigations, have arrived at a discovery that production of the mycelia can be greatly increased by the use of yeast extract as the nitrogen source in place of nitrates heretofore used. Further, they have separated the liquid culture medium containing the mycelia and the mycelia from the liquid culture medium and have discovered that the effective ingredients coming from the mycelia and contained in the culture medium and the mycelia can be served separately as such for food use leading to completion of the present invention on the base of this discovery.
Namely, the present invention provides a method for culturing an edible fungus characterized in that a liquid culture medium containing from 3 to 16 g/liter of sucrose and from 1 to 6 g/liter of maltose as the carbon source and from 0.3 to 1.2 g/liter of yeast extract as the nitrogen source is inoculated with an Agaricus mycelium and culturing is conducted under bubbling of sterilized air or oxygen-enriched air of an oxygen concentration of from 20 to 90%.